The invention applies particularly, but not exclusively, to a UMA (Unlicensed Mobile Access) network architecture. A UMA architecture enables users to use their mobile telephones on an IP (Internet Protocol) local area network when at home, at work or, more generally, in an area covered by an access point of an IP private mobile local area network, rather than using the chargeable fixed or mobile network of an operator.
Under the UMA standard, an approach of this kind has the advantage of significantly reducing call costs, especially for businesses, where the number of calls made by its staff is often high.
A simple illustrative and non-limiting example is the use a network architecture conforming to the UMA standard to extend GSM/GPRS mobile services in free access IP wireless networks (Wi-Fi™ or Bluetooth™ networks in particular) by creating a direct communication tunnel between a client communications terminal and the core network of the operator, with the following objectives:                enabling the user to use mobile voice and data services via private networks, retaining the same telephone number;        supporting handover between a private network and a GSM network;        remaining independent of the technology of the private network, for example the Wi-Fi™ or Bluetooth™ technology, while being transparent for existing units in the private network;        ensuring security equivalent to that of a GSM network.        
In the context of a residential UMA architecture (for example that deployed in the context of the Unik™ offer from Orange™), when an outgoing call request is generated by a GSM/GPRS-type communications network on a Wi-Fi™ network, a decision is taken relatively simply, in accordance with criteria defined beforehand by the mobile telephone operator.
If at the time of the call request the terminal is located in the coverage area of its Wi-Fi gateway, forming a unique access point to the network of the operator, then the Wi-Fi call is extended via the core network of the operator to the remote terminal for which the call is intended.
Otherwise, the outgoing call is switched to the chargeable GSM network of the operator automatically and without interruption (this procedure is usually known as “handover”).
Making such decisions proves incompatible with the use of a business-type UMA network architecture because, in such an architecture, the communication gateway serves as an interface between the private mobile local area network (of IP type, for example) of the business and the communications network of the operator. The gateway therefore needs to supervise and manage simultaneously a plurality of access points to the mobile local network, distributed over the site of the business, and must additionally manage a large number of calls by a large installed base of mobile communications terminals associated with the business's staff.
The maximum number of VoIP (Voice over IP) streams that a communications network can transmit at a given time, especially in a UMA architecture, proves to be an important parameter, representative of the level of quality of service (QoS) perceived by users.
If the number of VoIP streams in transit on the network at a given time exceeds this maximum number, the QoS offered to users is significantly degraded.
Also, one drawback of a UMA architecture comprising a plurality of mobile terminals (for example of the GSM, GPRS type) able to connect to a plurality of access points (AP) managed by a unique communication gateway (UMA gateway) enabling the IP private local area network of the business to interface with the core network of an operator, is primarily linked to the difficulty of being able to guarantee users and maintain a constant QoS, especially if there is a high influx of calls at a given time or over a given period.
Because of the large number of calls generated in the business on a daily basis, the maximum number of VoIP streams authorized by the operator will often be reached, with the consequence of degrading the quality of calls in transit via the UMA communication gateway.
In an attempt to address this problem, some technical approaches evaluate the maximum number of VoIP streams in transit at a given time in the WAN (Wide Area Network) of the UMA architecture, i.e. only on the operator core network side.
Such a prior art approach proves limited, however, in that it only partially addresses the above-mentioned drawbacks.
Although it is now possible for an operator to determine the maximum number of VoIP streams in transit on the WAN part of the network, either statically by recovering a predefined parameter value (maximum authorized VoIP streams), or dynamically, by means of a CAC (Call Admission Control) algorithm, with the objective of evaluating the possibility of adding a new stream, it is nevertheless impossible to evaluate the impact of adding any such new stream, end-to-end, both on the WAN part and, more importantly, on the WLAN part of a private mobile network. The degraded QoS of calls in a business-type UMA architecture stems most often from overloading said business's private mobile network.
What is more, in UMA architectures, there is no dynamic calculation of the number of VoIP streams, the WMM™ (Wireless MultiMedia) standard that aims to define criteria and methods of improving the quality of service rendered to wireless communication users specifying in its paragraph 3.5.2 (Version 1.1—Wi-Fi Alliance Technical Committee Quality of Service Task Group) that a method of determining the maximum VoIP stream value in a UMA architecture must be defined by each equipment manufacturer.
This situation contributes to the difficulty now encountered by operators and equipment manufacturers of being able to offer to businesses attractive and performing telephony solutions based on a UMA architecture.